I confess I know just about nothing in this area. :/
I do recommend you use UPS or FedEx. Don't use USPS.
Also here's a great video that exemplifies packaging.
I don't think it's winter packaging but it is packaging so it should give you a general idea.
You'll want to look up brands of heat packs and find out which ones are safe for fish and what not and how long they work for.
You'll definitely want overnight shipping or something of the sort.
Other than that I haven't the foggiest. Good luck with this.
Oh! And I've got a weird idea.....
Do you have any professors that you've gotten close to? Or have you tried talking to a professor in the marine biology department at your school?
Chances are they might sympathize with you and watch your boy if you paid them. =] It might actually cost less than shipping if money is tight.
just an idea though. =]
How long is your Winter Break?